Method of making a self-locking fastener



May 9, 1967 T. L. M KAY METHOD OF MAKING A SEL 3 Sheets-Sheet 1 OriginalFiled Feb 1967 T. 1.. M KAY METHOD OF MAKING A SELF'LOCKING FASTENER 5Sheets-Sheet 2 Original Filed Feb 1.2, 1964 May 9, 1967 T. L. M KAY3,317,938

METHOD OF MAKING A SELF-LOCKING FASTENER Original Filed Feb. 12, 1964 3Sheets-Sheet 5 United States Patent 3,317,938 METHOD OF MAKING ASELF-LDCKING FASTENER Thomas L. McKay, Los Angeles, Calif, assignor toLong- Lok Corporation, Los Angeles, Calif., a corporation of CaliforniaOriginal application Feb. 12, 1964, Ser. No. 344,329, now Patent No.3,263,726, dated Aug. 2, 1%6. Divided and this application Mar. 24,1966, Ser. No. 537,076 9 Claims. (CI. -10) This application is adivision of my copending application of the same title, Ser. No.344,329, filed Feb. 12, 1964, and now Patent No. 3,263,726.

This invention relates to a self-locking screw-threaded fastening memberof the type in which the self-locking action is achieved by means of aresiliently deformable plastic material. The fastening member may be ofthe general character of a screw for engagement by a complementary nut,or, conversely may be of the general character of a nut for engagementwith a complementary screw.

A self-locking screw threaded fastening member of this general type foruse with a cooperating element having a complementary thread mustachieve sufficiently effective frictional engagement with thecomplementary element to prevent loosening under the most adverseconditions, for example, conditions involving repeated varying stressand conditions involving high energy vibration. A common expedient forobtaining such frictional engagement is to insert a body of resilientlydeformable plastic material between the :screw thread of the fasteningmember and the complementary thread of the cooperating element. Thus aresilient deformable plastic insert may be added to a fastening membersuch as a screw for promoting frictional engagement with a cooperatingnut or may be added to a nut for promoting frictional engagement with acooperating screw. I

In the usual procedure for fabricating a self-locking fastening memberof this type, the fastening member is machined to provide some kind ofrecess for the resiliently deformable plastic body and the plastic bodyis installed in the recess. In a widely used construction, the recess isa longitudinal groove that intersects the turns of the screw thread forthe fastening member and is deeper than the screw thread.

The operation of cutting the groove represents a substantial portion ofthe fabrication cost and has the further disadvantage of materiallyweakening the fastening member. In addition, the insert must beinstalled in the groove in a separate operation and, finally, in manyinstances an additional operation is required to anchor theinstalledinsert in the recess.

The present invention teaches that the preliminary machining of thefastening member to form a recess may be completely eliminated. Thus theinvention not only simplifies the fabrication procedure for costreduction but also avoids weakening the screw. The invention furtherteaches that the resiliently deformable plastic body may be installed inonly one operation if desired.

The invention is based on the concept of placing an elongatedresiliently deformable plastic body longiuldinally of the threadedportion of the fastening member, forcing the plastic body into the screwthread with consequent penetration of the plastic body by the turns ofthe screw thread as well as consequent displacement of portions of theplastic body into the valleys of the turns of the screw thread, and,while the plastic material is under compression, deforming the crests ofthe turns of the screw thread adjacent the plastic material in suchmanner that the deformations overhang the valleys of the turns of thescrew thread to retain the displaced plastic portions in the valleys.

In some practices of the invention, this operation is performed in twosteps, the first step being to force plastic material into engagementwith the screw thread by means of one tool, the second step being to usea second tool to place the engaged body again under pressure andsimultaneously to deform the crests of the turns of the screw threads toretain the plastic portions. A feature of other practices, however, isthat the whole operation is carried out in a single step in which asuitable tool drives the plastic body into the screw thread and with thesame stroke makes the deformations in the turns of the screw thread foranchoring the plastic material.

The invention further teaches that such an insert may be installed insubstantially the same manner by dies that are employed primarily toform the screw thread by a rolling operation. In such an operation ablank screw confined between two relatively moving dies rolls along onedie as the screw thread is formed. For the purpose of the presentinvention the plastic insert is appropriately placed in the path of therolling screw to be picked up by the formed screw thread and then theformed screw thread i is deformed in a manner to anchor the plasticmaterial.

The various features and advantages of the invention may be understoodfrom the following detailed description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a side elevational view of a screw with an elongated body ofresiliently deformable plastic material positioned longitudinal of thescrew across the turns of the screw thread in preparation for carryingout the method taught by the invention;

FIG. 2 is an end elevation of the assembly shown in FIG. 1;

FIG. 3 is a transverse sectional view showing how the plastic body isdriven into the turns of the screw thread and at the same time somewhatflattened;

FIG. 4 is a similar view showing how die means operates on the assemblyshown in FIG. 3 to compress the insert body laterally and to deform theturns of the screw thread to confine the compressed plastic material;

FIG. 5 is a transverse sectional view similar to FIG. 4 showing how adifferent die may be used to carry out the second operation;

FIG. 6 is an enlarged transverse cross section of the completedself-locking screw;

FIG. 7 is a plan view of the completed self-locking screw;

FIG. 8 is an enlarged fragmentary perspective view showing the manner inwhich the deformations of the turns of the screw thread retain theplastic material;

FIG. 9 is a fragmentary enlarged plan view showing the deformations ofthe turns of the screw thread without the plastic material;

FIG. 10 shows an elongated plastic body positioned on a screw inpreparation for installing the plastic body in a single operation by apair of dies, the dies being shown in open position;

FIG. 11 is a similar view with the dies closed to complete theoperation;

FIG. 12 is an enlarged fragmentary plan view showing a portion of thecompleted self-locking screw as produced by the method shown in FIGS. 11and 12;

FIG. 12a is a fragmentary section taken along the line 12a-l2a of FIG.12;

FIG. 13 is a sectional view showing how dies may be employed in anotherpractice of the invention;

FIG. 14 is a fragmentary sectional view on an enlarged scale showing thecompletion of the operation that is started in FIG. 13;

FIG. is a greatly enlarged fragmentary perspective view showing theresult of the method illustrated by FIGS. 13 and 14; V

FIG. 16 is a diagrammatic elevation-a1 view showing how an operation ofrolling a screw thread into a screw blank may be utilized in onepractice of the invention;

FIG. 17 is a plan view of the structure shown in FIG. 16;

FIG. 18 is an enlarged sectional view of a portion of the structureshown in FIGS. 16 and 17 with a plastic body positioned to be picked upby the screw thread of the rolling screws; and

FIG. 19 is a similar sectional view showing how a die may be used tocompress the plastic material and simultaneously deform the turns of thescrew thread.

FIGS. 1 and 2 show a well known type of screw, generally designated bythe letter S, the shank of the screw being formed with a conventionalscrew thread 20. FIGS. 1 and 2 further show an elongated body 22 ofresiliently deformable plastic material of the configuration of a shortrod which is positioned longitudinally of the shank of the screw along adesired longitudinal Zone. The plastic material may be nylon, forexample. With the elongated body of the plastic in this position, thescrew S is placed in a lower die 24 which functions as a solid supportfor the screw and then an upper die 25 is reciprocated against theinsert body to drive the plastic material into turns of the screw threadand at the same time to flatten the plastic material to the generallyoval cross-sectional configuration shown in FIG. 3.

The upper die 25 has a cylindrically curved concave leading face 26which conforms at least approximately to the curvature of the screwthread 20. Preferably the leading face 26 does not completely closeagainst the crests of the turns of the screw thread 20 so that theresult of the die operation is a series of portions of the plasticmaterial seated in the valleys of the turns of the screw thread with theportions interconnected outside of the outside diameter of the screwthread. In other words, preferably the insert body is not crowded by thedie face 25 to such extent as to cause the turns of the screw thread todivide the insert material into completely discrete portions.

With the screw S still seated in the lower die 24 the lower die is movedto a new station where an upper die 28 cooperates with the lower die tocomplete the fabrication of the self-locking screw. The upper die 28 hasa leading face 30 of concave cylindrical curvature which conforms to thecurvature of the screw thread 20 and this leading face has alongitudinal flat portion 32 which is broken by a central longitudinalgroove 34. When the upper die 28 closes against the lower die 24 asshown in FIG. 4 two fiat areas of the upper die 28 on opposite sides ofthe groove 34 impinge on the crests of the turns of the screw thread todeform the screw thread, the result being two spaced rows ofdeformations 35 as shown in FIGS. 7 and 9. At the same time, the groove34 in the upper die forms the plastic material into a longitudinal rib36 shown in FIGS. 7 and 8.

The two rows of deformations 35 lie on opposite sides of a longitudinalradial plane that bisects the rib 36 longitudinally, the radial planebeing indicated by the dotted lines 38 in FIGS. 6 and 9. It is to benoted that the deformations 35 in the two rows flare towards the radialplane 38. It is also to be noted that the deformations 35 are spread orextended longitudinally of the screw to overhang the valleys of theturns of the screw thread 20 and thereby permanently retain the portionsof the plastic material that are displaced into the valleys.

It is important to note that when the upper die 28 creates thedeformations 35 it simultaneously compresses the plastic materialagainst the periphery of the screw with the consequence that thedeformations hold portions of the anchored plastic under compression. Itis also to be noted, as shown in FIGS. 7 and 8, that each pair of thesuccessive deformations 35 in each of the two rows of the twodeformations form a portion of the plastic material into a dove-tail 40,the dove-tail engagement being highly effective topreventcircumferential shift of the portions of the plastic material.

Since the plastic material that forms the longitudinal rib 36 projectsoutwardly beyond the circumference of the crests of the screw thread 20,portions of the turns of the screw thread 20 are imbedded in the rib 36slightly below the outer surface of the rib as may be seen in FIG. 8.

FIG. 5 shows how an upper die 42 may be substituted for the upper die 28of FIG. 4 in carrying out the second step of the operation. The upperdie 42 differs from the upper die 28 in having a broad fiat leading face44 with a longitudinal groove 45 formed in the face. The result ofclosing the die 42 against the lower die 24 is substantially the same asthe result of closing the upper die 28 against the lower die 24.

It has been found that the use of the first upper die 25 may be omitted,the whole fabrication procedure being carried out with one stroke of thesecond upper die 28. Thus the screw S with the plastic insert body 22positioned thereon may be placed in the lower die 24 and the fabricationprocedure may be carried out solely by the second upper die 28. In sucha practice of the invention the upper die 28 serves in one stroke todrive the plastic material into the turns of the screw thread and todeform the screw thread for anchorage of the plastic material. Thesingle operation produces exactly the same product as the operation intwo steps. The upper die 42 shown in FIG. 5 may also be used inconjunction with the lower die 24 to carry out the whole fabricationprocedure in a single step.

FIGS. 10 and 11 show how an upper die 46 may cooperate with the lowerdie 24 to carry out a fabrication procedure in a single step. The upperdie 46 is like the upper die 42 of FIG. 5 but has a flat face 48 that isnot interrupted by a longitudinal groove. When the upper die 46 closesagainst the lower die 24 as shown in FIG. 11, the flat upper face 48invades the outer circumference of the screw thread 20 and therebydeforms the turns of the screw thread in the manner indicated in FIGS.12 and 12a. As shown in FIG. 12 the flat die face 48 producesdeformations 50 in each turn of the screw thread, which deformation isof oval configuration in plan. Thus each of the deformation 50 flarestowards a central radial plane indicated by dotted lines 52 in FIGS. 11and 12. The initially round plastic body 22 is flattened as indicated inFIG. 11 and, as indicated in FIG. 12a the turns of the screw threaddivide the plastic body into discrete smaller bodies and thedeformations 50 of the turns of the screw thread spread or expandlongitudinally of the screw to overhang the valleys of the screw threadto retain the plastic material therein.

FIGS. 13 to 15 illustrate a practice of the invention in which theinitially round plastic body is processed in two steps to produce thefinal product shown in FIGS. 14 and 15.

FIG. 13 shows the screw S positioned in the previously described lowerdie 24 for processing in sequence by a central upper die 52 and a pairof cooperating upper dies 54. The upper die 52 has a leading face 55 ofcylindrically curved configuration with relatively short radius ofcurvature to cause the plastic body 22 be flattened to the ovalconfiguration shown in FIG. 13. After the upper die 52 is retracted, thepair of dies 54 converge downward in the directions of the two arrows56. As shown in FIG. 14 the pair of dies 54 come together andsimultaneously penetrate the material of the turns of the screw thread20 to produce the final product.

It can be seen in FIG. 14 that when the pair of dies 54 close togetherthey form a flat leading face 58 that is broken by a longitudinal groove60. It is to be noted that the longitudinal groove 60 is of dove-tailedcrosssectional configuration so that the longitudinal die edges 62 thatare formed by the groove are relatively sharp edges. As shown in FIG. 15the dies 54 create flared deformations 64 in the turns of the screwthread that are similar in general to the previously mentioneddeformations 35. It may also be seen in FIG. 15 that the final producthas a longitudinal plastic rib 65 in which portions of the turns of thescrew thread are imbedded.

FIGS. 16 to 19 illustrate another practice of the invention in which thescrew thread 66 of a screw S is produced by a rolling action and thedies for carrying out the rolling operation are involved in theapplication of the plastic material to the screw.

The rolling operation is carried out in the usual manner by placing aheaded screw blank 68 on a lower die 70 and then rolling the screw blankalong the lower die by means of a cooperating upper die 72. The two diesare formed in the usual manner with parallel ribs 74 to create thedesired helical screw thread. At a point on the lower die 70 slightlybeyond the point where the formations of the screw thread is completed,the ribs 74 on the lower die terminate and a transverse groove 75 isprovided to seat a previously mentioned plastic insert body 22. When thefinished screw approaches the insert body 22 as shown in FIG. 18, theturns of the screw thread 66 that is formed by the rolling operationpenetrate. the plastic body 22 to cause the rolling screw to pick up theplastic body. Placing the insert body 22 in the groove 75 keeps theturns of the screw thread 66 from cutting entirely through the insertbody.

The rolling of the finished screw stops with the insert body 22uppermost as shown in FIG. 19 and a simple flat die 76 is advancedagainst the screw in the region of the insert to form oval deformationsof the configuration of the previously described deformations 50 in FIG.12.

My description in specific detail of the selected practices of theinvention will suggest various changes, substitutions and otherdepartures from my disclosure within the spirit and scope of theappended claims.

I claim:

1. A method of equipping a screw-threaded fastener with deformableresilient plastic material for self-locking action, characterized by thesteps of:

placing an elongated body of the plastic material in a positiongenerally longitudinally of the fastener over the crests of the turns ofthe screw thread;

displacing the elongated plastic body towards the root diameter of thescrew thread with consequent penetration of the plastic body by theturns of the screw thread and consequent insertion of portions of theplastic body into the valleys of the turns of the screw thread; and

applying force to the crests of the turns of the screw thread along theregion of the displaced plastic material to make deformations in theturns of the screw thread with the deformations overhanging the valleysto retain the portions of the plastic material in the valleys.

2. A method of equipping a screw-threaded fastener with deformableresilient plastic material for self-locking action, characterized by thesteps of:

placing an elongated body of the plastic material in a positiongenerally longitudinally of the fastener over the crests of the turns ofthe screw thread; and applying die means against the outer side of theplastic body and moving the die means towards the root diameter of thescrew thread into impact with the crests of the turns of the screwthread to cause the turns of the screw thread to penetrate the plasticbody and to force portions of the plastic body into the valleys of theturns of the screw thread and to make deformations in the turns of thescrew thread with the deformations overhanging the valleys to retain theportions of plastic material in the valleys.

3. A method as set forth in claim 2 in which the die means has alongitudinal recess in its leading face dimensioned to straddle aportion of the displaced plastic material whereby the die means onopposite sides of the recess forms two spaced rows of deformations inthe turns of the screw thread.

4. A combination as set forth in claim 3 in which said recess in the diemeans is of a depth to clear the crests of the turns of the screw threadwhen the die means forms the two rows of deformations.

5. A method as set forth in claim 2 in which the die means has asubstantially flat uninterrupted leading face.

6. A method of equipping a screw-threaded fastener with deformableresilient plastic material for self-locking action, characterized by thesteps of:

placing an elongated body of the plastic material in a positiongenerally longitudinally of the fastener over the crests of the turns ofthe screw thread;

applying a member against the outer side of the plastic body and movingthe member towards the root diameter of the screw thread with consequentpenetration of the plastic body by the turns of the screw thread andconsequent displacement of portions of the plastic body into the valleysof the turns of the screw; and

then applying die means against the outer side of the plastic body andmoving the die means towards the root diameter of the screw threadagainst the crests of the turns of the screw thread to make deformationsin the turns of the screw thread and to cause the deformations tooverhang the valleys to retain the portions of the plastic body in thevalleys.

7. A method as set forth in claim 6 in which the die means has alongitudinal recess in its leading face dimensioned to straddle aportion of the displaced plastic material whereby the die means onopposite sides of the recess forms two spaced rows of deformations inthe turns of the screw thread.

8. A method as set forth in claim 6 in which the die means is made intwo sections which travel on convergent paths to make the deformationsin the turns of the screw thread.

9. A method of fabricating a screw with deformable plastic materialassembled thereto to make the screw selflocking, characterized by thesteps of:

rolling a screw blank between two dies to form a screw thread thereon;

positioning an elongated body of deformable resilient plastic materialon one of the two dies in the path of the rolling screw blank with theplastic body substantially parallel with the screw blank to cause theformed screw thread to penetrate the plastic body and pick up theplastic body; and

then applying pressure to the outer side of the plastic body and toportions of the turns of the screw thread adjacent the plastic body toforce portions of the plastic body into the valleys of the turns of thescrew thread and to make deformations in the turns of the screw threadto overhang the valleys to retain the portions of the plastic body inthe valleys.

References Cited by the Examiner UNITED STATES PATENTS 3,020,570 2/1962Wallace et a1 1010 3,093,177 6/1963 Villo 1517 WILLIAM W. DYER, JR.,Primary Examiner. LE NIDAS VLACHOS, Examiner.

1. A METHOD OF EQUIPPING A SCREW-THREADED FASTENER WITH DEFORMABLERESILIENT PLASTIC MATERIAL FOR SELF-LOCKING ACTION, CHARACTERIZED BY THESTEPS OF: PLACING AN ELONGATED BODY OF THE PLASTIC MATERIAL IN APOSITION GENERALLY LONGITUDINALLY OF THE FASTENER OVER THE CRESTS OF THETURNS OF THE SCREW THREAD; DISPLACING THE ELONGATED PLASTIC BODY TOWARDSTHE ROOT DIAMETER OF THE SCREW THREAD WITH CONSEQUENT PENETRATION OF THEPLASTIC BODY BY THE TURNS OF THE SCREW THREAD AND CONSEQUENT INSERTIONOF PORTIONS OF THE PLASTIC BODY INTO THE VALLEYS OF THE TURNS OF THESCREW THREAD; AND APPLYING FORCE TO THE CREST OF THE TURNS OF THE SCREWTHREAD ALONG THE REGION OF THE DISPLACED PLASTIC MATERIAL TO MAKEDEFORMATIONS IN THE TURNS OF THE SCREW THREAD WITH THE DEFORMATIONSOVERHANGING THE VALLEYS TO RETAIN THE PORTIONS OF THE PLASTIC MATERIALIN THE VALLEYS.